How Computer Display Technologies Work - Part 3

DVI-D: True Digital Video. Unlike standard VGA cables, DVI-D transfers and all digital signal from one source to another. While standard video cards do produce a digital signal, they convert this signal to an analog signal at the VGA connection which is then reconverted back to digital at the monitor or other connecting device. DVI-D does away with the conversion process altogether since the signal is 100% digital from point A to point B. The DVI-D connection consists of 2 sets of 9 pins that are separated apart from each other, followed by a flat horizontal blade (view the diagrams). This is the “Single Link” DVI-D connector. This type of DVI-D uses “Transmission Minimized Differential Signaling” or TMDS. TMDS is a digital signaling protocol that uses a 165MHz signal transmitter to send data. The DVI-D single link connector uses one TMDS transmitter, while the DVI-D dual link uses two. The dual link DVI-D connector consists of 3 rows of 8 pins as well as a solid blade. Dual link connectors effectively double the transmission power, providing an effective increase in speed and signal quality. DVI-D single link can transmit display resolutions up to 1920X1200, while DVI-D dual link can transmit at resolutions up to 2560X1600. While this is arguably a better connection, in which I can agree it's definitely a cleaner image, it may cause problems for individuals who are partially visually impaired. This seems to be what I found personally after working for years helping people with their computer and monitor issues. Make sure the technology you put in place works for your clients, you will avoid repeat phone calls and having to deal with repeat problems this way.

DVI-I: (DVI Integrated) This type of DVI connector can transmit both DVI analog or DVI digital signals. However, it cannot transmit digital to analog or analog to digital signals, they can only do one or the other. DVI-D connectors cannot be used with DVI-A (analog) connections. Likewise, DVI-A connectors cannot be used with DVI-D connections. DVI-I connectors consist of both single link and dual link configurations. The single link DVI-I connector consists of 2 sets of 9 pins that are separated and 1 blade, but also has 4 additional pins (2 on top of the blade and 2 underneath it). DVI-I dual link consists of 3 rows of 8 pins and 4 additional pins as before (2 on top of the blade and 2 underneath it).

DVI-A: (DVI Analog) This type of DVI connector transmits high bandwidth analog signals. This connector consists of one set of 8 pins, 2 sets of 2 pins on the far right, and a blade with 4 pins (2 on top of the blade and 2 underneath it).

Remember, you cannot connect a digital DVI connection and analog one, and vice-versa. The DVI-I is great for one you have multiple devices set up in various uses that use both technologies. This connector gives you the ability to use it on either digital or analog, instead of just digital, or just analog such as with DVI-D or DVI-A.

S-Video: Although sometimes referred to as “Super Video”, this is actually wrong, it means Separate Video. It uses a 4 or 7 pin mini din connector. This protocol works by carrying just 2 data streams, a Y stream for luminescence (brightness), and a C stream for chrominance (color).

Composite Video: an analog video format that carries a Y signal (brightness), and U and V signals (color/chrominance). It uses an RCA connector and is found on older model desktop and laptop PC’s. Most computers today have done away with this protocol in favor of HDMI, although virtually all current PC models still have a VGA DB15 connection.

Component Video: Is an older RGB format for carrying analog video. Its broken up into Red, Green, and Blue data streams. With component video, the RGB signal is converted to a compressed video signal, allowing for the use of less bandwidth. Red: Pr, Blue: Pb, and Green: Y. The Y signal is for luminance, the second and third signals are “color difference” signals. The red (Pr) signal signifies the difference between Luminance Y and color (in this case red), resulting in a R-Y designation. The blue signal works the same way, This signal also signifies the difference between luminance and color. Blue (Pb) and Y for luminance equates to B-Y. Component video provides for a fast video data stream as the RGB signal is compressed to the component format. Component typically uses an RCA style connector, although some older professional video equipment used a BNC style connector. BNC (bayonet nut coupling) sometimes referred to as a british naval connector as well.

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